The invention relates to display devices, and more particularly, to display systems with digitizers.
Many types of touch sensitive computer input devices are currently touched on or in conjunction with computer displays. Such devices detect the position of a position pointer or finger contact on the sensor surface. The position coordinates are generated for interaction with the computer, for example in selecting icons on the display, menu items, editing images, or feedback for input of hand-drawn characters and graphics.
Numbers of technologies can be used for such devices, including capacitive sensing, resistive sensing using a conductive overlay sheet, infrared sensing, acoustic wave sensing, and piezoelectric force sensing. One of such device like digitizers which use hardwired handheld position pointer such as pens typically use electromagnetic, electrostatic, resistive, or sonic pulse sensing.
These input devices responsive to human contact are typically used for cursor control, such as selection of display icons and menu items. Other input devices responsive to position pointer (usually a hardwired pen) are used to create or trace drawings, blueprints, or original art. These devices are also used for character or handwriting recognition. It is therefore desirable that the sensor reproduce the path of the position pointer by some visual means to provide visual feedback.
Some of these input devices are responsive to both user and position pointer contact, thereby providing the convenience of position pointer-based input, for example when writing on the screen, as well as the ease of touch input, which does not require position pointer.
FIG. 1 is a structural diagram of a conventional display device with a digitizer. As shown, the display device 200 comprises a top glass cover 210, liquid crystal display (LCD) panel 220, a backlighting module 230, a reflector 240, digitizer sensor board 250, a shield film 260, a back frame 270 and a position pointer 280. The top glass cover 210, the LCD panel 220, the backlighting module 230, the reflector 240, the digitizer sensor board 250, the shield film 260 and the back frame 270 are assembled as a laminated construction. The LCD panel 220 and the digitizer sensor board 250 are coupled to an external host system via differential interfaces, such as two flexible printed circuit boards (FPCs). FIG. 2 is a block diagram of a conventional display system with a digitizer. As shown, display system 100 comprises LCD module 220 and digitizer module 250. The LCD module 220 and the digitizer module 250 are coupled to the host system 130 via corresponding interfaces 112 and 122 respectively. The digitizer module 250 requires an oscillator 124 disposed in the microcontroller 126 to generate scan timing signals (SS) for the selection circuit 128, thereby performing scan operation of sensor array 129. Because the reflector, the digitizer sensor board, a shield film and a back frame in the conventional display system are separate components and the LCD module and the digitizer module require differential interfaces coupled to an external host system, the conventional display system presents increased costs, thickness, and weight.